The present invention relates to recycling of a plasma display panel (hereinafter referred to as xe2x80x9cPDPxe2x80x9d) employed in a computer terminal, a wall-hung television, and the like. More particularly, the invention relates to a method of disassembling a PDP, as well as a structure of a PDP and a method of heating the PDP, with which the disassembling is made efficiently.
PDPs are self-luminous displays that are easily viewable from a wide range of angles, advantageously very thin and large in screen area size. For these reasons, PDPs are becoming ever more popular as new display devices that are replacing cathode ray tubes (CRTs). Since surface-discharge type AC PDPs, in particular, are easy to manufacture, and have a long operational life, many of them have been developed, manufactured, and marketed by numerous manufacturers.
As shown in FIG. 16, a PDP comprises a front plate 1 and a back plate 2 consisting of a glass substrate 3 and provided on front plate 1 are sustain electrodes 5, a dielectric layer 6 and a protection layer 7. Back plate 2 consists of a second glass substrate 4 and provided on it are address electrodes 8, and barrier ribs 9. Further, phosphor 10 is provided within the ribs 9. Both plates are bonded together along their entire periphery with bonding material 13.
An ordinary manufacturing process of the PDPs can be broken down into the steps of (a) producing front plates, (b) producing back plates, (c) assembling, sealing, vacuuming and gas charging.
When producing a front plate 1, sustain electrodes 5 are formed on a glass substrate 3, and a dielectric layer 6 made of low temperature-melting glass containing lead oxide is formed on glass substrate 3 by screen-printing and sintering.
A back plate 2 is produced by forming address electrodes 8 on a glass substrate 4, and ribs 9 between the address electrodes 8 with low temperature-melting glass containing lead oxide. Phosphors 10 of red, green and blue colors are formed between the ribs 9.
The front plate 1 and the back plate 2 are assembled together by placing one over the other, and hermetically bonding them with bonding material 13 containing lead oxide. A PDP is finally completed by charging it with a rare gas containing Xe, after a sufficient discharge of impure gases by vacuum-pumping an interior, while heating the assembled PDP.
As described, the PDPs use a considerable amount of low temperature-melting glass containing lead oxide. Low temperature-melting glass is used for the dielectric layer in the front plate, the ribs in the back plate, and the bonding material for hermetically bonding the front plate with the back plate, to name a few examples. These PDPs are disposed of, if any flaw is detected in them during the manufacturing process, or when they have lost their usable life in their end use application. However, they cannot be discarded like ordinary waste products, but they are required to be treated properly by establishments specializing in industrial waste disposal, because they contain lead.
Although there is a way to recycle the discarded PDPs as glass cullet for manufacturing glass, the discarded PDPs propound a problem of degrading quality of glass, if mixed with raw glass material, since they contain lead oxide.
Additionally, there is a need for taking urgent measures against disposal of products containing lead components, in view of the recent global environmental issues and strict regulations against lead waste.
The present invention utilizes a thermal action and a chemical action in a process of disassembling the above-described PDPs.
A first method adopts a component, that does not contract thermally at a softening temperature of a bonding material used for hermetically bonding a front plate to a back plate, and is positioned between the two plates at the front and back. And, the two plates are separated with the use of this component. Further, the above-cited component maintains a gap with either one of the front plate and the back plate under an ambient room temperature, but the component either remains unchanged dimensionally, or expands when heated, thereby the component facilitates disassembly of the PDP.
Furthermore, the present invention provides a groove on at least one of the surfaces of the front plate and the back plate, for communicating the bonding material to an exterior of the PDP. A softened bonding material can be drawn out or absorbed through the groove. Another feature of the invention is to uniformly heat and cool the PDP with a laminated graphite sheet provided on either an upper surface or a side surface of the PDP during the heating process.
A second method of the present invention is to separate a PDP into two glass substrates by immersing the PDP in etching solution that selectively dissolves only lead glass, and melts the bonding material.
For this method, a groove is formed in a space between a perimeter of an image display screen and a bonded portion, in order to prevent the etching solution from invading into the display area in a center of the PDP by a capillary phenomenon. In either case of the front plate and the back plate, the groove is formed in a direction parallel with a longitudinal direction of electrodes formed on the substrates.
The front plate and the back plate which are separated through the foregoing process are refurbished in a way that a deteriorated portion or a defective portion regains an original function. The refurbished front plate and back plate can be reutilized to make a PDP by hermetically bonding them again. Therefore, the handling and disposal of dangerous lead materials may be significantly reduced thereby materially enhancing the quality of the environment.